1. Technical Field
It is known to assess a network having a main line and a plurality of branch lines by introducing a test signal into the main line and monitoring a return signal that arises due to the reflection or the backscattering of the test signal along the branch lines. An analysis of the return signal is performed to ascertain whether there are any faults or losses along the branch lines. However, if the return signal suggest a fault, it can be difficult to determine which branch line is responsible for the fault. In particular, as the number of branch lines increases it becomes increasingly difficult even to detect that there is a fault.
2. Related Art
According to the present exemplary embodiment, there is provided a method of assessing an optical network having a main line and a plurality of branch lines, the method including the steps of: (i) introducing test signals into the main line, the main line being coupled to the branch lines in a branching fashion such that the test signals propagate along the branch lines; (ii) imposing a modulation on test signals which propagate along a designated branch line; and (iii) monitoring test signals returned along the main line, the imposed phase modulation being detected interferometrically such that the test signals from the designated branch line can be distinguished with respect to the signals returned from other branch lines.